diff --git a/LDDsimulation/boundary_and_interface.py b/LDDsimulation/boundary_and_interface.py
index 76b78db1b475e02ccbe6b088112653785c5ca96f..48f6ea7f6127059fd081c287fc8122a7fd6b1129 100644
--- a/LDDsimulation/boundary_and_interface.py
+++ b/LDDsimulation/boundary_and_interface.py
@@ -177,11 +177,6 @@ class BoundaryPart(df.SubDomain):
         xmax = max(p1[0], p2[0])
         ymin = min(p1[1], p2[1])
         ymax = max(p1[1], p2[1])
-        # print(f"test if point {p} is on line segment between {p1} or {p2}")
-        # check if p == p1 or p == p2
-        if np.fabs((p[0] - xmax)*(p[0] - xmin)) < tol and np.fabs((p[1] - ymax)*(p[1] - ymin)) < tol:
-            #print(f"point {p} is close to either {p1} or {p2}")
-            return True
 
         # check there holds p1[0] < p[0] < p2[0]. If not, p  cannot be on the line segment
         # same needs to be done for p1[1] < p[1] < p2[1]
@@ -609,16 +604,24 @@ class Interface(BoundaryPart):
         # of edges on the boundary. We need the number of nodes, however.
         number_of_interface_vertices = sum(interface_marker.array() == interface_marker_value) + 1
 
+        print(f"interface marker array",interface_marker.array() == interface_marker_value)
+        print(f"facets marked by interface marker", interface_marker.array())
+        print(f"interface{self.global_index} has coordinates {self.coordinates(interface_marker, interface_marker_value)}")
+        # for cell in interface_marker[interface_marker.array() == interface_marker_value]:
+        #     print(cell.get_cell_data())
         # print(f"\nDetermined number of interface vertices as {number_of_interface_vertices}")
         # we need one mesh_dimension + 1 columns to store the the index of the node.
         vertex_indices = np.zeros(shape = number_of_interface_vertices, dtype=int)
         # print(f"allocated array for vertex_indices\n", vertex_indices) #
         interface_vertex_number = 0
         # mesh_vertex_index = 0
+        print(f"\n we are one interface{self.global_index}",
+              f" we determined {number_of_interface_vertices} interface vertices.")
         for vert_num, x in enumerate(mesh_coordinates):
             if self._is_on_boundary_part(x):
                 # print(f"Vertex {x} with index {vert_num} is on interface")
                 # print(f"interface_vertex_number = {interface_vertex_number}")
+                print(f"dfPoint = ({x}) is on interface{self.global_index}")
                 vertex_indices[interface_vertex_number] = vert_num
                 interface_vertex_number += 1
 
diff --git a/RR-multi-patch-plus-gravity/RR-multi-patch-with-gravity.py b/RR-multi-patch-plus-gravity/RR-multi-patch-with-gravity.py
index d1375f3936e370f9348313538e1558d60131f66f..16d3d63d8f45f1dce24b35ba11b2d5eda34ebb70 100755
--- a/RR-multi-patch-plus-gravity/RR-multi-patch-with-gravity.py
+++ b/RR-multi-patch-plus-gravity/RR-multi-patch-with-gravity.py
@@ -15,15 +15,15 @@ sym.init_printing()
 # ----------------------------------------------------------------------------#
 # ------------------- MESH ---------------------------------------------------#
 # ----------------------------------------------------------------------------#
-mesh_resolution = 30
+mesh_resolution = 3
 # ----------------------------------------:-------------------------------------#
 # ------------------- TIME ---------------------------------------------------#
 # ----------------------------------------------------------------------------#
 timestep_size = 0.01
-number_of_timesteps = 500
+number_of_timesteps = 1
 # decide how many timesteps you want analysed. Analysed means, that we write
 # out subsequent errors of the L-iteration within the timestep.
-number_of_timesteps_to_analyse = 11
+number_of_timesteps_to_analyse = 0
 starttime = 0
 
 
diff --git a/TP-TP-layered-soil-case-with-inner-patch/TP-TP-layered_soil_with_inner_patch.py b/TP-TP-layered-soil-case-with-inner-patch/TP-TP-layered_soil_with_inner_patch.py
new file mode 100755
index 0000000000000000000000000000000000000000..b7294621b4e7e42270a38bc6f352972e65b8d1c7
--- /dev/null
+++ b/TP-TP-layered-soil-case-with-inner-patch/TP-TP-layered_soil_with_inner_patch.py
@@ -0,0 +1,569 @@
+#!/usr/bin/python3
+"""This program sets up a domain together with a decomposition into subdomains
+modelling layered soil. This is used for our LDD article with tp-tp and tp-r
+coupling.
+
+Along with the subdomains and the mesh domain markers are set upself.
+The resulting mesh is saved into files for later use.
+"""
+
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import functools as ft
+import domainPatch as dp
+import LDDsimulation as ldd
+
+# init sympy session
+sym.init_printing()
+
+# ----------------------------------------------------------------------------#
+# ------------------- MESH ---------------------------------------------------#
+# ----------------------------------------------------------------------------#
+mesh_resolution = 5
+# ----------------------------------------:-----------------------------------#
+# ------------------- TIME ---------------------------------------------------#
+# ----------------------------------------------------------------------------#
+timestep_size = 0.003
+number_of_timesteps = 300
+# decide how many timesteps you want analysed. Analysed means, that we write
+# out subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 11
+starttime = 0
+
+l_param_w = 80
+l_param_nw = 120
+
+# global domain
+subdomain0_vertices = [df.Point(0.0,0.0), #
+                        df.Point(13.0,0.0),#
+                        df.Point(13.0,8.0),#
+                        df.Point(0.0,8.0)]
+
+interface12_vertices = [df.Point(0.0, 7.0),
+                        df.Point(9.0, 7.0),
+                        df.Point(10.5, 7.5),
+                        df.Point(12.0, 7.0),
+                        df.Point(13.0, 6.5)]
+# subdomain1.
+subdomain1_vertices = [interface12_vertices[0],
+                        interface12_vertices[1],
+                        interface12_vertices[2],
+                        interface12_vertices[3],
+                        interface12_vertices[4], # southern boundary, 12 interface
+                        subdomain0_vertices[2], # eastern boundary, outer boundary
+                        subdomain0_vertices[3]] # northern boundary, outer on_boundary
+
+# vertex coordinates of the outer boundaries. If it can not be specified as a
+# polygon, use an entry per boundary polygon. This information is used for defining
+# the Dirichlet boundary conditions. If a domain is completely internal, the
+# dictionary entry should be 0: None
+subdomain1_outer_boundary_verts = {
+    0: [interface12_vertices[4], #
+        subdomain0_vertices[2], # eastern boundary, outer boundary
+        subdomain0_vertices[3],
+        interface12_vertices[0]]
+}
+
+
+# interface23
+interface23_vertices = [df.Point(0.0, 5.0),
+                        df.Point(3.0, 5.0),
+                        # df.Point(6.5, 4.5),
+                        df.Point(6.5, 5.0),
+                        df.Point(9.5, 5.0),
+                        # df.Point(11.5, 3.5),
+                        # df.Point(13.0, 3)
+                        df.Point(11.5, 5.0),
+                        df.Point(13.0, 5.0)
+                        ]
+
+#subdomain1
+subdomain2_vertices = [interface23_vertices[0],
+                        interface23_vertices[1],
+                        interface23_vertices[2],
+                        interface23_vertices[3],
+                        interface23_vertices[4],
+                        interface23_vertices[5], # southern boundary, 23 interface
+                        subdomain1_vertices[4], # eastern boundary, outer boundary
+                        subdomain1_vertices[3],
+                        subdomain1_vertices[2],
+                        subdomain1_vertices[1],
+                        subdomain1_vertices[0] ] # northern boundary, 12 interface
+
+subdomain2_outer_boundary_verts = {
+    0: [interface23_vertices[5],
+        subdomain1_vertices[4]],
+    1: [subdomain1_vertices[0],
+        interface23_vertices[0]]
+}
+
+
+
+interface32_vertices = [interface23_vertices[2],
+                        interface23_vertices[1],
+                        interface23_vertices[0]]
+
+interface34_vertices = [df.Point(4.0, 2.0),
+                        df.Point(4.7, 3.0),
+                        interface23_vertices[2]]
+# interface36
+interface36_vertices = [df.Point(0.0, 2.0),
+                        df.Point(4.0, 2.0)]
+
+subdomain3_vertices = [interface36_vertices[0],
+                       interface36_vertices[1],
+                       interface34_vertices[0],
+                       interface34_vertices[1],
+                       interface34_vertices[2]
+                       interface32_vertices[0],
+                       interface32_vertices[1],
+                       interface32_vertices[2]
+                       ]
+
+interface46_vertices = [df.Point(4.0, 2.0),
+                        df.Point(9.0, 2.5)]
+
+interface46_vertices = [df.Point(9.0, 2.5),
+                        df.Point(10.5, 2.0),
+                        df.Point(13.0, 1.5)]
+
+# subdomain3
+subdomain3_vertices = [interface34_vertices[0],
+                        interface34_vertices[1],
+                        interface34_vertices[2],
+                        interface34_vertices[3],
+                        interface34_vertices[4], # southern boundary, 34 interface
+                        subdomain2_vertices[5], # eastern boundary, outer boundary
+                        subdomain2_vertices[4],
+                        subdomain2_vertices[3],
+                        subdomain2_vertices[2],
+                        subdomain2_vertices[1],
+                        subdomain2_vertices[0] ] # northern boundary, 23 interface
+
+
+
+
+subdomain3_outer_boundary_verts = {
+    0: [interface34_vertices[4],
+        subdomain2_vertices[5]],
+    1: [subdomain2_vertices[0],
+        interface34_vertices[0]]
+}
+
+# subdomain4
+subdomain4_vertices = [subdomain0_vertices[0],
+                        subdomain0_vertices[1], # southern boundary, outer boundary
+                        subdomain3_vertices[4],# eastern boundary, outer boundary
+                        subdomain3_vertices[3],
+                        subdomain3_vertices[2],
+                        subdomain3_vertices[1],
+                        subdomain3_vertices[0] ] # northern boundary, 34 interface
+
+subdomain4_outer_boundary_verts = {
+    0: [subdomain4_vertices[6],
+        subdomain4_vertices[0],
+        subdomain4_vertices[1],
+        subdomain4_vertices[2]]
+}
+
+
+subdomain_def_points = [subdomain0_vertices,#
+                      subdomain1_vertices,#
+                      subdomain2_vertices,#
+                      subdomain3_vertices,#
+                      subdomain4_vertices
+                      ]
+
+
+# interface_vertices introduces a global numbering of interfaces.
+interface_def_points = [interface12_vertices, interface23_vertices, interface34_vertices]
+adjacent_subdomains = [[1,2], [2,3], [3,4]]
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    1: subdomain1_outer_boundary_verts,
+    2: subdomain2_outer_boundary_verts,
+    3: subdomain3_outer_boundary_verts,
+    4: subdomain4_outer_boundary_verts
+}
+
+isRichards = {
+    1: False,
+    2: False,
+    3: False,
+    4: False
+    }
+
+# Dict of the form: { subdom_num : viscosity }
+viscosity = {
+    1: {'wetting' :1,
+         'nonwetting': 1/50},
+    2: {'wetting' :1,
+         'nonwetting': 1/50},
+    3: {'wetting' :1,
+         'nonwetting': 1/50},
+    4: {'wetting' :1,
+         'nonwetting': 1/50},
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    1: {'wetting': 997,
+         'nonwetting': 1.225},
+    2: {'wetting': 997,
+         'nonwetting': 1.225},
+    3: {'wetting': 997,
+         'nonwetting': 1.225},
+    4: {'wetting': 997,
+         'nonwetting': 1.225}
+}
+
+gravity_acceleration = 9.81
+# porosities taken from
+# https://www.geotechdata.info/parameter/soil-porosity.html
+# Dict of the form: { subdom_num : porosity }
+porosity = {
+    1: 0.2,  # Clayey gravels, clayey sandy gravels
+    2: 0.22, # Silty gravels, silty sandy gravels
+    3: 0.37, # Clayey sands
+    4: 0.2 # Silty or sandy clay
+}
+
+# subdom_num : subdomain L for L-scheme
+L = {
+    1: {'wetting' :0.3,
+         'nonwetting': 0.25},
+    2: {'wetting' :0.3,
+         'nonwetting': 0.25},
+    3: {'wetting' :0.3,
+         'nonwetting': 0.25},
+    4: {'wetting' :0.3,
+         'nonwetting': 0.25}
+}
+
+# subdom_num : lambda parameter for the L-scheme
+lambda_param = {
+    1: {'wetting': l_param_w,
+         'nonwetting': l_param_nw},#
+    2: {'wetting': l_param_w,
+         'nonwetting': l_param_nw},#
+    3: {'wetting': l_param_w,
+         'nonwetting': l_param_nw},#
+    4: {'wetting': l_param_w,
+         'nonwetting': l_param_nw},#
+}
+
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+
+## relative permeabilty functions on subdomain 2
+def rel_perm2w(s):
+    # relative permeabilty wetting on subdomain2
+    return s**3
+
+
+def rel_perm2nw(s):
+    # relative permeabilty nonwetting on subdosym.cos(0.8*t - (0.8*x + 1/7*y))main2
+    return (1-s)**2
+
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+_rel_perm2w = ft.partial(rel_perm2w)
+_rel_perm2nw = ft.partial(rel_perm2nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+subdomain2_rel_perm = {
+    'wetting': _rel_perm2w,#
+    'nonwetting': _rel_perm2nw
+}
+
+# _rel_perm3 = ft.partial(rel_perm2)
+# subdomain3_rel_perm = subdomain2_rel_perm.copy()
+#
+# _rel_perm4 = ft.partial(rel_perm1)
+# subdomain4_rel_perm = subdomain1_rel_perm.copy()
+
+# dictionary of relative permeabilties on all domains.
+relative_permeability = {
+    1: subdomain1_rel_perm,
+    2: subdomain1_rel_perm,
+    3: subdomain2_rel_perm,
+    4: subdomain2_rel_perm
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*(1-s)
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm2w_prime(s):
+    # relative permeabilty on subdomain1
+    return 3*s**2
+
+def rel_perm2nw_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+_rel_perm2w_prime = ft.partial(rel_perm2w_prime)
+_rel_perm2nw_prime = ft.partial(rel_perm2nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+
+subdomain2_rel_perm_prime = {
+    'wetting': _rel_perm2w_prime,
+    'nonwetting': _rel_perm2nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    1: subdomain1_rel_perm_prime,
+    2: subdomain1_rel_perm_prime,
+    3: subdomain2_rel_perm_prime,
+    4: subdomain2_rel_perm_prime
+}
+
+
+
+# S-pc-relation ship. We use the van Genuchten approach, i.e. pc = 1/alpha*(S^{-1/m} -1)^1/n, where
+# we set alpha = 0, assume m = 1-1/n (see Helmig) and assume that residual saturation is Sw
+# this function needs to be monotonically decreasing in the capillary pressure pc.
+# since in the richards case pc=-pw, this becomes as a function of pw a mono
+# tonically INCREASING function like in our Richards-Richards paper. However
+# since we unify the treatment in the code for Richards and two-phase, we need
+# the same requierment
+# for both cases, two-phase and Richards.
+def saturation(pc, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + (alpha*pc)**n_index)**((n_index - 1)/n_index)), 1)
+
+# S-pc-relation ship. We use the van Genuchten approach, i.e. pc = 1/alpha*(S^{-1/m} -1)^1/n, where
+# we set alpha = 0, assume m = 1-1/n (see Helmig) and assume that residual saturation is Sw
+def saturation_sym(pc, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    #df.conditional(pc > 0,
+    return 1/((1 + (alpha*pc)**n_index)**((n_index - 1)/n_index))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    return -(alpha*(n_index - 1)*(alpha*pc)**(n_index - 1)) / ( (1 + (alpha*pc)**n_index)**((2*n_index - 1)/n_index) )
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    1: ft.partial(saturation_sym, n_index=3, alpha=0.001),
+    2: ft.partial(saturation_sym, n_index=3, alpha=0.001),
+    3: ft.partial(saturation_sym, n_index=6, alpha=0.001),
+    4: ft.partial(saturation_sym, n_index=6, alpha=0.001)
+}
+
+S_pc_sym_prime = {
+    1: ft.partial(saturation_sym_prime, n_index=3, alpha=0.001),
+    2: ft.partial(saturation_sym_prime, n_index=3, alpha=0.001),
+    3: ft.partial(saturation_sym_prime, n_index=6, alpha=0.001),
+    4: ft.partial(saturation_sym_prime, n_index=6, alpha=0.001)
+}
+
+sat_pressure_relationship = {
+    1: ft.partial(saturation, n_index=3, alpha=0.001),
+    2: ft.partial(saturation, n_index=3, alpha=0.001),
+    3: ft.partial(saturation, n_index=6, alpha=0.001),
+    4: ft.partial(saturation, n_index=6, alpha=0.001)
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+p_e_sym = {
+    1: {'wetting': 1.0 - (1.0 + t*t)*(10.0 + x*x + (y-5.0)*(y-5.0)),
+        'nonwetting': - 2 - t*(1 + (y-5.0) + x**2)**2 -sym.sqrt(2+t**2)*(1 + (y-5.0)) },
+    2: {'wetting': 1.0 - (1.0 + t*t)*(10.0 + x*x + (y-5.0)*(y-5.0)),
+        'nonwetting': - 2 - t*(1 + (y-5.0) + x**2)**2 -sym.sqrt(2+t**2)*(1 + (y-5.0))},
+    3: {'wetting': 1.0 - (1.0 + t*t)*(10.0 + x*x + (y-5.0)*(y-5.0)*3*sym.sin(-2*t+2*x)*sym.sin(1/2*y-1.2*t)),
+        'nonwetting': - 2 - t*(1 + x**2)**2 -sym.sqrt(2+t**2)},
+    4: {'wetting': 1.0 - (1.0 + t*t)*(10.0 + x*x + (y-5.0)*(y-5.0)*3*sym.sin(-2*t+2*x)*sym.sin(1/2*y-1.2*t)),
+        'nonwetting': - 2 - t*(1 + x**2)**2 -sym.sqrt(2+t**2)}
+}
+
+pc_e_sym = {
+    1: p_e_sym[1]['nonwetting'] - p_e_sym[1]['wetting'],
+    2: p_e_sym[2]['nonwetting'] - p_e_sym[2]['wetting'],
+    3: p_e_sym[3]['nonwetting'] - p_e_sym[3]['wetting'],
+    4: p_e_sym[4]['nonwetting'] - p_e_sym[4]['wetting']
+}
+
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+dtS = dict()
+div_flux = dict()
+source_expression = dict()
+exact_solution = dict()
+initial_condition = dict()
+for subdomain, isR in isRichards.items():
+    dtS.update({subdomain: dict()})
+    div_flux.update({subdomain: dict()})
+    source_expression.update({subdomain: dict()})
+    exact_solution.update({subdomain: dict()})
+    initial_condition.update({subdomain: dict()})
+    if isR:
+        subdomain_has_phases = ["wetting"]
+    else:
+        subdomain_has_phases = ["wetting", "nonwetting"]
+
+    # conditional for S_pc_prime
+    pc = pc_e_sym[subdomain]
+    dtpc = sym.diff(pc, t, 1)
+    dxpc = sym.diff(pc, x, 1)
+    dypc = sym.diff(pc, y, 1)
+    S = sym.Piecewise((S_pc_sym[subdomain](pc), pc > 0), (1, True))
+    dS = sym.Piecewise((S_pc_sym_prime[subdomain](pc), pc > 0), (0, True))
+    for phase in subdomain_has_phases:
+        # Turn above symbolic expression for exact solution into c code
+        exact_solution[subdomain].update(
+            {phase: sym.printing.ccode(p_e_sym[subdomain][phase])}
+            )
+        # save the c code for initial conditions
+        initial_condition[subdomain].update(
+            {phase: sym.printing.ccode(p_e_sym[subdomain][phase].subs(t, 0))}
+            )
+        if phase == "nonwetting":
+            dS = -dS
+        dtS[subdomain].update(
+            {phase: porosity[subdomain]*dS*dtpc}
+            )
+        pa = p_e_sym[subdomain][phase]
+        dxpa = sym.diff(pa, x, 1)
+        dxdxpa = sym.diff(pa, x, 2)
+        dypa = sym.diff(pa, y, 1)
+        dydypa = sym.diff(pa, y, 2)
+        mu = viscosity[subdomain][phase]
+        ka = relative_permeability[subdomain][phase]
+        dka = ka_prime[subdomain][phase]
+        rho = densities[subdomain][phase]
+        g = gravity_acceleration
+
+        if phase == "nonwetting":
+            # x part of div(flux) for nonwetting
+            dxdxflux = -1/mu*dka(1-S)*dS*dxpc*dxpa + 1/mu*dxdxpa*ka(1-S)
+            # y part of div(flux) for nonwetting
+            dydyflux = -1/mu*dka(1-S)*dS*dypc*(dypa - rho*g) \
+                + 1/mu*dydypa*ka(1-S)
+        else:
+            # x part of div(flux) for wetting
+            dxdxflux = 1/mu*dka(S)*dS*dxpc*dxpa + 1/mu*dxdxpa*ka(S)
+            # y part of div(flux) for wetting
+            dydyflux = 1/mu*dka(S)*dS*dypc*(dypa - rho*g) + 1/mu*dydypa*ka(S)
+        div_flux[subdomain].update({phase: dxdxflux + dydyflux})
+        contructed_rhs = dtS[subdomain][phase] - div_flux[subdomain][phase]
+        source_expression[subdomain].update(
+            {phase: sym.printing.ccode(contructed_rhs)}
+            )
+        # print(f"source_expression[{subdomain}][{phase}] =", source_expression[subdomain][phase])
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+write_to_file = {
+    'meshes_and_markers': True,
+    'L_iterations': True
+}
+
+# initialise LDD simulation class
+simulation = ldd.LDDsimulation(tol=1E-14, debug=True, LDDsolver_tol=1E-7)
+simulation.set_parameters(output_dir="./output/",
+                          subdomain_def_points=subdomain_def_points,
+                          isRichards=isRichards,
+                          interface_def_points=interface_def_points,
+                          outer_boundary_def_points=outer_boundary_def_points,
+                          adjacent_subdomains=adjacent_subdomains,
+                          mesh_resolution=mesh_resolution,
+                          viscosity=viscosity,
+                          porosity=porosity,
+                          L=L,
+                          lambda_param=lambda_param,
+                          relative_permeability=relative_permeability,
+                          saturation=sat_pressure_relationship,
+                          starttime=starttime,
+                          number_of_timesteps=number_of_timesteps,
+                          number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                          timestep_size=timestep_size,
+                          sources=source_expression,
+                          initial_conditions=initial_condition,
+                          dirichletBC_expression_strings=dirichletBC,
+                          exact_solution=exact_solution,
+                          densities=densities,
+                          include_gravity=True,
+                          write2file=write_to_file,
+                          )
+
+simulation.initialise()
+# print(simulation.__dict__)
+simulation.run()
+# simulation.LDDsolver(time=0, debug=True, analyse_timestep=True)
+# df.info(parameters, True)
diff --git a/TP-TP-layered-soil-case/TP-TP-layered_soil.py b/TP-TP-layered-soil-case/TP-TP-layered_soil.py
index 7ecf9a728e057af3f5a92fd17fd9be9da67b59b6..2cfac5c1df658a4b5817832aa0d54a1a67158884 100755
--- a/TP-TP-layered-soil-case/TP-TP-layered_soil.py
+++ b/TP-TP-layered-soil-case/TP-TP-layered_soil.py
@@ -23,19 +23,19 @@ sym.init_printing()
 # ----------------------------------------------------------------------------#
 # ------------------- MESH ---------------------------------------------------#
 # ----------------------------------------------------------------------------#
-mesh_resolution = 4
+mesh_resolution = 20
 # ----------------------------------------:-------------------------------------#
 # ------------------- TIME ---------------------------------------------------#
 # ----------------------------------------------------------------------------#
-timestep_size = 0.005
-number_of_timesteps = 30
+timestep_size = 0.003
+number_of_timesteps = 300
 # decide how many timesteps you want analysed. Analysed means, that we write
 # out subsequent errors of the L-iteration within the timestep.
 number_of_timesteps_to_analyse = 11
 starttime = 0
 
-l_param_w = 40
-l_param_nw = l_param_w
+l_param_w = 80
+l_param_nw = 120
 
 # global domain
 subdomain0_vertices = [df.Point(0.0,0.0), #
@@ -213,13 +213,13 @@ porosity = {
 
 # subdom_num : subdomain L for L-scheme
 L = {
-    1: {'wetting' :0.25,
+    1: {'wetting' :0.3,
          'nonwetting': 0.25},
-    2: {'wetting' :0.25,
+    2: {'wetting' :0.3,
          'nonwetting': 0.25},
-    3: {'wetting' :0.25,
+    3: {'wetting' :0.3,
          'nonwetting': 0.25},
-    4: {'wetting' :0.25,
+    4: {'wetting' :0.3,
          'nonwetting': 0.25}
 }
 
@@ -492,13 +492,11 @@ dirichletBC = dict()
 
 # subdomain index: {outer boudary part index: {phase: expression}}
 for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
     if outer_boundary_def_points[subdomain] is None:
         dirichletBC.update({subdomain: None})
     else:
         dirichletBC.update({subdomain: dict()})
-    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
-
-    if outer_boundary_def_points[subdomain] is not None:
         # set the dirichlet conditions to be the same code as exact solution on
         # the subdomain.
         for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
@@ -512,7 +510,7 @@ write_to_file = {
 }
 
 # initialise LDD simulation class
-simulation = ldd.LDDsimulation(tol=1E-14, debug=False, LDDsolver_tol=1E-9)
+simulation = ldd.LDDsimulation(tol=1E-14, debug=True, LDDsolver_tol=1E-7)
 simulation.set_parameters(output_dir="./output/",
                           subdomain_def_points=subdomain_def_points,
                           isRichards=isRichards,